Bake for 30 minutes in the preheated oven. Meanwhile, combine 1/3 cup sugar, 1/3 cup flour, and cinnamon in a small bowl. Cut in butter with fork or pastry blender until mixture resembles coarse crumbs. Set aside.

Remove pie from oven. Reduce oven temperature to 350F. Sprinkle topping mixture evenly over pie. Return pie to oven and bake until filling is set and crust and topping are golden brown, about 30 minutes.